British Patent 1 273 023 discloses an electric radiant heater, whose heating means has a heating resistor operated with a very high glow temperature, which is encapsulated in the manner of a halogen radiator in a quartz glass tube, which is curved in the manner of a circular arc. This light radiator is used for heating a glass ceramic plate.
U.S. Pat. No. 4,700,051 discloses the use of both light and dark radiators within a radiant heater. Preferably the dark radiator is always connected upstream of the light radiator and the dark radiator damps the high starting current of the light radiator. Arrangements are provided in which outside substantially parallel, rod-like light radiators, dark radiators are provided so as to externally surround the same. German Utility model 8525 366 also describes such an arrangement.
However, according to U.S. Pat. No. 4,700,051 circular light radiators always pass round in the outer marginal zone, so as to also optically limit or define the heating zone on the glass ceramic plate, because the latter is partly transparent at least in the case of the strong radiating action of the light radiator.
Despite their relatively high price, bent light radiators were developed in order to make it possible in a single passage round the outer area of the radiant heater to provide the total light radiator power leaving the central zone for the more surface acting dark radiators. It has been found that the glow pattern and other use characteristics, together with the ease of manufacture are not ideal.